2026 ICD-10-CM Diagnosis Code C57.21Malignant neoplasm of right round ligament

ICD-10-CM Codes›C00–D49›C51-C58›C57

ICD-10-CM C57.21
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

C57.21 is a billable ICD-10-CM diagnosis code for malignant neoplasm of right round ligament. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 736 through 741, 754 through 756. Coders also document this condition as malignant neoplasm of round ligament. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Female reproductive system cancers - all other types.

Code Identity

ICD-10-CM Code
C57.21
Billable Status
Yes — Valid for Submission
Code Describes
Malignant neoplasm of right round ligament
Short Description
Malignant neoplasm of right round ligament
Same as the full description in the CMS dataset.
Parent Code
C57.2
Malignant neoplasm of round ligament

Code Classification

ChapterC00–D49Neoplasms
SectionC51-C58Malignant neoplasms of female genital organs
CategoryC57Malignant neoplasm of other and unspecified female genital organs
This CodeC57.21Malignant neoplasm of right round ligament

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Malignant neoplasm of round ligament
  • Neoplasm of round ligament of uterus
  • Primary malignant neoplasm of pelvic peritoneum
  • Primary malignant neoplasm of right round ligament
  • Primary malignant neoplasm of round ligament of uterus

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NEO038
Female reproductive system cancers - all other types
Default principal diagnosis: inpatient Yes · outpatient Yes

Table of NeoplasmsClinical

Anatomical sites in the Table of Neoplasms that reference this code family.

SiteMalig.
Primary		Malig.
Secondary		Ca
in situ		BenignUncertainUnspec.
ligament [See Also: Neoplasm, connective tissue] › roundC57.2C79.82–D28.2D39.8D49.59
round ligamentC57.2C79.82–D28.2D39.8D49.59
uterus, uteri, uterine › ligament › roundC57.2C79.82–D28.2D39.8D49.59

Patient EducationClinical

Uterine Cancer

Uterine cancer is a cancer that forms in tissues of the uterus, which is sometimes called the womb. The uterus is the place where a fetus grows during pregnancy.

The full article covers:

  • What is uterine cancer?
  • Who is more likely to develop uterine cancer?
  • What are the symptoms of uterine cancer?
  • How is uterine cancer diagnosed?
  • What are the treatments for uterine cancer?
  • Can uterine cancer be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert C57.21 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
183.5 Mal neo round ligament
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About C57.21Overview

Is C57.21 (Malignant neoplasm of round ligament) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report malignant neoplasm of right round ligament on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does C57.21 group to?

When malignant neoplasm of right round ligament is the principal diagnosis on an inpatient stay, it groups to MS-DRG 736, 737, 738, 739, 740, 741, 754, 755, 756, with relative weights from 0.9605 to 3.5745 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of C57.21?

Under the General Equivalence Mappings, malignant neoplasm of right round ligament converts to ICD-9-CM 183.5 (mal neo round ligament). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.